Background radiation levels, health

For comparison, we have calculated the health effects for typical residential properties (4 occupants each) based on 1) the naturally occurring background radiation levels and radionuclide concentrations in four cities across the U.S. (see Table V) and 2) the EPA (CFR, 1981) guideline values (20 yR/h, 0.02 WL, 5 pCi Ra-226/g of soil) for cleanup at inactive uranium processing sites (see Table VI). 

Table V. Lifetime Health Effects Estimates at Background Radiation Levels for a Typical Residential Property in Several U.S. Cities...

For comparison, the health effects calculated from exposure to natural background radiation levels for typical residential properties were all about 0.01 per property, with radon daughters accounting for more than 50% of the total health effects estimated. 

The National Coimcil for Radiation Protection (NCRP) has identified a negligible individual risk level (NIRL) as a level of annual excess risk of health effects attributable to irradiation below which further effort to reduce radiation to the individual is unwarranted. The NCRP emphasized that this level should not be confused with an acceptable risk level, a level of significance or a standard. The NCRP recommended a level around half the natural background radiation level the final recommended NIRL level is 1 mrem this level is now called negligible individual dose (NID) level (Harley, 2001, 2008). 

Health physics is concerned with protection of people from radiation. Since the background radiation has been, is, and will always be on our planet at about the same level everywhere, there is not much a health physicist can do to protect individuals or populations from background radiation. Hence, health physics is concerned with protection of people from man-made radiation. 

Current opinion is that there is a small risk to human health from even low levels of exposure to ionizing radiation, but there is also a known quantity of natural background radiation that the human species has always encountered. In 1984, an employee at a nuclear power plant began to set off radiation alarms while walking into the plant. An investigation found that his home contained high levels of radon gas from natural minerals. Radon tests are now routinely performed in many homes. 

How is the actual incidence of cancer caused by radiation exposure actually related to the total incidence of cancer, and can it be reduced One study (235) showed that of the total number of cancer fatalities in the United States in 1975 resulting from radiation, only 2.7 percent of the ongoing exposures would result in low-level radiation-induced cancer fatalities. Most arise from natural background radiation or medical exposures. The only significant change that could be made to alter this number is to attempt to modify the incidence of medical exposure. Since most exposures to medical radiation are undertaken to benefit the individual, and presumably other adverse health effects would result as a consequence of withholding the exposure, limiting medical exposures would probably not reduce the total overall mortality. 

The human body is equipped to deal with nominal levels of radiation doses. Background (natural) radiation from radon gas, cosmic sources, soil, and water produces an average dose of about 0.3 rem (0.003 Sv) per year.4 However, large doses of radiation generated after a terrorist attack can overwhelm the body s ability to repair damage, leading to stochastic or acute health effects. 

If levels of radiation above natural background are discovered, a plant manager should consult a health physicist. At levels greater than 2 mrem/hour, aU industrial site activities should cease until the site has been assessed by an industrial health scientist or licenced environmental engineers. 

The creation of our world occurred in intense radiation Helds and, consequently, we have inherited an Earth drenched in radiation from cosmic sources and the minerals in the groimd (Ch. S, 10 and 17). Though the intensity of these radiation sources is much smaller than produced by human techniques, no human can avoid these natural sources. Therefore, the effects of the natural radiation background has become an important health issue, particularly radon levels in houses. Closely related to this problem is the effects of man-made sources of similarly low levels, such as the storage of nuclear waste. Much research is presently devoted to the effects of low-level radiation. 

Three basic principles are recommended for keeping radiation exposure to a minimum shielding, control, and distance. If a radiochemical laboratory is designed properly and the work performed in such a manner that the g eral background contamination is suffici tly low to do valid low level tracer experiments, then the health aspects of radiation control are satisfied. We indicate the main principles for work with radioactive substances, but in each notion, special rules may apply. 

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